Merge pull request TheAlgorithms#220 from TheAlgorithms/changed_parenthesis.c

BUG fix data_structures/stack/parenthesis.c

Author: Christian Bender

data_structures/stack/balanced parenthesis using stack in C

@@ -0,0 +1,115 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#define SIZE 100
+
+struct node
+{
+    char data;
+    struct node *link;
+};
+
+int c = 0;         // c used as counter to check if stack is empty or not
+struct node *head; //declaring head pointer globally assigned to NULL
+
+void push(char x) //function for pushing
+{
+    struct node *p = head, *temp;
+    temp = (struct node *)malloc(sizeof(struct node));
+    temp->data = x;
+    if (head == NULL) //will be execute only one time i.e, 1st time push is called
+    {
+        head = temp;
+        p = head;
+        p->link = NULL;
+        c++;
+    }
+    else
+    {
+        temp->link = p;
+        p = temp;
+        head = p;
+        c++;
+    }
+}
+
+char pop(void) //function for pop
+{
+    char x;
+    struct node *p = head;
+    x = p->data;
+    head = p->link;
+    free(p);
+    c--;
+    return x;
+}
+
+int isBalanced(char *s)
+{
+    int i = 0;
+    char x;
+    while (s[i] != '\0') //loop for covering entire string of brackets
+    {
+        // printf("\t s[i]=%c\n", s[i]); //DEBUG
+        if (s[i] == '{' || s[i] == '(' || s[i] == '[') //if opening bracket then push
+            push(s[i]);
+        else
+        {
+            if (c <= 0) //i.e, stack is empty as only opening brackets are added to stack
+                return 0;
+
+            x = pop();
+            if (x == '{' && s[i] != '}')
+                return 0;
+            if (x == '[' && s[i] != ']')
+                return 0;
+            if (x == '(' && s[i] != ')')
+                return 0;
+        }
+        i++;
+    }
+
+    //at end if stack is empy which means whole process has been performed correctly so return 1
+    return (c == 0) ? 1 : 0;
+}
+
+void destroyStack(void)
+{
+    struct node *p = head;
+    if (c > 0)
+    {
+        while (p->link)
+        {
+            struct node *tmp = p;
+            p = p->link;
+            free(tmp);
+        }
+
+        c = 0;
+    }
+}
+
+int main(void)
+{
+    int t;
+    printf("\t\tBalanced parenthesis\n\n");
+    printf("\nPlease enter the number of processing rounds? ");
+    scanf("%d", &t);
+    for (int a0 = 0; a0 < t; a0++)
+    {
+        char s[SIZE];
+        printf("\nPlease enter the expression? ");
+        scanf("%s", s);
+
+        if (isBalanced(s))
+            printf("\nYES\n");
+        else
+            printf("\nNO\n");
+
+        /* tidy up stack for new round */
+        destroyStack();
+    }
+    return 0;
+}